Hydrogeological studies continue to refine subsoil modeling

Rising global temperatures and the increasing frequency of droughts both underline a crucial fact: water is a precious asset. In France, nearly two-thirds of drinking water come from groundwater resulting from the infiltration of rainwater. These resources can also be used to meet the needs of agricultural and industrial activities.

In the context of the EMILI project, the mine’s operation (rock extraction) would not use any water. However, the treatment of the rock to extract lithium will require water resources, but it will be reused as much as possible through recycling circuits. Furthermore, depending on the location and depth of the extraction zone, the extraction process may alter either the underground water circuits or the water’s composition.

All these challenges led Imerys to contract Antea Group, an international consulting firm specializing in environmental engineering, to carry out various hydraulic and hydrogeological studies across the entire Bosse massif. These studies are intended to pursue several different goals:

• modeling surface and subsoil flows to determine the precise amount and circulation of water resources,
• analyzing this water to establish its physicochemical characteristics in advance of the project,
• identifying potential impacts of underground extraction on water circulation and quality with the aim of improving prevention measures.

Monitoring over a full year to model the massif

The conclusions of these studies will make it possible to evaluate and then to simulate the impact of the EMILI project, in both quantitative and qualitative terms. In practical terms, over one hundred monitoring points (private wells, waterways, etc.) have been mapped at various distances from the quarry and in different environments in order to obtain representative data. "Installing piezometers – devices for measuring the level and pressure of water – will complete the network of these monitoring points", explains Fabrice Frebourg, environmental project manager at Imerys. "Regular measurements of water flow and quality are carried out at the most representative points." Begun last winter, the monitoring campaign will continue through the end of 2023 in order to provide an initial model of the massif over an annual cycle.

This model will be enriched over subsequent years. "We need to take into account in our studies the atypical years as well as the context of global warming", notes Fabrice Frebourg. "These studies will thus continue over the long term. The goal is to understand how water circulates in the upper formations and possibly in the underlying granite, and in what quantity."

This data is essential for identifying the potential interactions of future lithium extraction galleries with the underground water circulation or possible infiltrations, with the aim of preventing any change in water quality. The goal is also to avoid damaging aquatic environments and other water use by the community or activities like agriculture.

Working with local stakeholders

As Boris Vaxelaire, environmental project manager for Imerys, explains, studies by Antea experts are carried out in consultation with local stakeholders in charge of water resources, such as "the Local Water Commission (CLE), the coordinator of the Water Management and Development Framework (SAGE), other relevant government services, and the SIVOM unions, who manage domestic and industrial water supply circuits. This collective work allows for the collection of quantitative data and a history of water flow rates and uses at the local level."

Following the conclusions delivered by Antea Group, Imerys can base its work on this data that is shared with local stakeholders. "If necessary, we are also open to third-party analysis to verify the methodology of these studies. Our goal is to operate the site in a planned manner and in safe environmental conditions", concludes Fabrice Frebourg.